Fuel burning and flame detection means



-Fb.5,19s3 w. A. RAY mL 3,076,495

FUEL BURNING AND FLAME DETECTIQN MEANS Filed June 19, 1961 jira-1 30 FR/V465 FUEL CNT/PL SYSTEM r.FGT 2 u H 7 TORNEFS United States Patent "O FUEL BURNING AND FLAME DETECTION MEANS William A. Ray, North Hollywood, Calif., and Justin A. Deubel, Hales Corners, and Milton H. McCormick, Milwaukee, Wis., assiguors to General Controls Co.,

Glendale, Calif., a corporation of California Filed June 19, 1961, Ser. No. 118,184

8 Claims. (Cl. 158-28) The present invention relates to flame detection means involving the use of a cell such as, for example, a cadmium sulphide'type cell which is used to control the ow of fuel to an oil burner.

Cadmium sulphide type cells have heretofore been proposed for the purposes of flame detection or indication and/ or the control of fuel to a burner with means found necessary for effectively amplifying the output of the cell to achieve these purposes.

In accordance with one important feature of the present invention, means and techniques are provided whereby these purposes are achieved without amplification means, ie. an indication or control functionv is realized using the resistance changes inthe cell directly.

In achieving these purposes, a cadmium sulphide type cell is associated with a special optical system involving quartz or Vicor glass rods in an assembly positioned to transmit tiame radiation through such rods from the ame to the cell.

.The present invention is particularly useful for sensing a llame in oil burning equipment. Another important feature of the present invention involves the particular placement of the cell and its radiation transparent rods in relationship to the burner such that sufficient radiation vimpinges on the cell while at the same time the same is not overheated to 'such an extent as to unduly shorten its life. VAnother important feature of the present invention is to provide a radiation reflective coating on such radiation conducting rods such that dirt, carbon deposits and the like thereon after prolonged use produce no substantial change in radiation transmitted by such rods.

Another important feature of the present invention is to provide an arrangement of this character wherein the radiation-transmitting tube of quartz projects into the flame area to burn carbon deposits therefrom while at the same time the cell is not overheated.

Another important feature of the present invention is to provide an arrangement of this character wherein the cell is mounted in the blast tube itself.

It is therefore an object of the present invention to provide means and techniques whereby these above-indicated features are realized.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following `description taken in connection with the accompanying drawings in which:

FIGURE l illustrates a system embodying features of the present invention.

FIGURE 2 illustrates a view taken in the direction of the arrows 2-2 in FIGURE 1.

FIGURE 3 illustrates modified detecting means which may be substituted for the detecting means in FIGURE 1.

FIGURE 4 illustrates a modification in which the radiation transparent rod is coated to provide a mirror finish for preserving the internal reflections characteristic of the rod.

In one form of the invention illustrated in FIGURE 1, a cadmium sulphide cell is mounted by suitable means inside of the blast tube 12 either on the upstream or 3,076,495 Patented Feb. 5, 1963 ICC downstream side of the conventional combustion air twirling vanes 13 in tube 12, although in some cases the blast tube may be provided without twirling vanes. Fuel oil is supplied through conduit 14 to the burner nozzle 15 which in conventional manner is located just inside the choke ring 16. A radiation-conducting quartz rod 17 has one of its ends aligned or optically coupled with the lightreceiving-end of cell 10 and the other one of its ends extending through the choke ring 16 where the same may attain a temperature of approximately 1100 Fahrenheit or more so that any carbon deposits may -be burned from the projecting end of rod 17.

Because the rod 17 is subjected to high temperatures, the rod 17 is sufficiently prolonged so that the cell 10 is positioned for suicient heat dissipation. As shown, the cell is positioned in the path of combustion air which serves to cool the same as Well as the adjacent portion of the radiation-transmitting rod 17. Also, preferably the cell is located such that a static shield is interposed between the burner nozzle 15 and cell 10 to prevent direct radiation between the region of the nozzle 15 and cell 10. Such shield as shown is the cup-shaped shield 20 which is apertured for mounting on the oil supply conduit 14 and also apertured for mounting the spark electrode 22 Which is used for igniting the fuel when the burner is initially placed in operation. While this shield 20 is in the path of direct flame radiation, the same is also cooled by combustion air ilowing through the blast tube.

I-t has been found `that accumulated dust or dirt on the sides of rod 17 impairs its light-transmission properties and to assure substantially the same light-transmission properties in prolonged use, the rod 17 is preferably provided with a mirror-like coating 4i), as illustrated in FIG- URE 4, so that radiation in the tube is not otherwise ab- `sorbe'd by such dust or dirt. Such a mirror coating may comprise aluminum foil. suitablybonded to the tube 17 along its full length.

In some cases, instead of using quartz or Vicor exclusively as the radiation-transmitting element, a section of Pyrex rod 24 as shown in FIGURE 3 may be used interposed between quartz rod 26 and cell 10. It has been found that the Pyrex rod has the advantage of absorbing most of the radiation in the infrared region, thereby reducing considerably the temperature of cell 10. The Pyrex rod 24, however, does not transmit useful radiation in other portions of the spectrum as well as quartz and for that reason it is preferred not to use long lengths of Pyrex rod. Also, when using rods of different materials as shown in FIGURE 3, care is required to achieve good optical coupling between abutting ends of the Pyrex rod 24 and quartz or Vicor rod 26.

In some cases that end of the radiation transparent rod adjacent the cell 10 may be in mechanical abutment with the window of cell 10 and in other cases the same may be spaced a slight distance therefrom to allow mounting of an adjustable iris 28 as shown in FIGURE 3, particularly when an assembly is provided for universal mounting in diiferent types of oil burner blast tubes.

While it is preferred to mount the assembly inside of the burner blast tube as shown in FIGURE 1 since it has been found that the response of the cell is very fast to llame conditions, the assembly may be mounted outside of the blast tube with the extreme end of the radiation-transmitting rod projecting into the furnace 29 and with the cell positioned outside of the furnace 29 where it -is cooled. In the latter case, however, it is found that the response of the cell is not as fast since a large amount of radiation from the refractory material delining the inside of the furnace 29 impinges on the rod and thus serves to obscure or override that radiation from the ame itself.

It has also been found that after extensive use some devitrication occurs at the end of quartz rod 17 but the same does not materially decrease the light transmission when, as shown, the rod 17 is installed in a burner blast tube with such rod end projecting past the choke ring 16 a distance of approximately one-half of one inch (1/2").

In each one of the arrangements the cell may be connected electrically, as illustrated in FIGURE l, to provide either a control function or an indicating function.

Thus, in FIGURE l the cell 10 is energized with a rectified A.C. current supplied from a 11S-volt A.C. source 30 which has its terminals connected to the primary winding of step-down transformer 31. The secondary Winding is connected in series with the relay coil 32, rectifier 33 and cell 10, the coil 32 being shunted by a lll-microfarad condenser 33 for prolonging the drop-out time of the relay having coil 32 and associated relay switches 32A and 32B so that the control is not operated by transient conditions, i.e. flame llicker or flutter. When a 'flame is present, the flame radiation impinging on cell 10 lowers its resistance and maximum current flows through coil 32 with the result that the normally closed relay switch 32A is open and the normally closed relay switch 32B is closed. Swith 32A is connected to a conventional fuel burner control system 36 which controls the supply of fuel to the burner conduit 14. When switch 32A is open, fuel is permitted to flow to the burner but when switch 32A is closed (when there is no llame) the flow of fuel is automatically interrupted by control system 36. Likewise, when switch 32B is closed (when there is no llame), this condition, i.e. llame failure, is indicated by indicating lamp 40 which is connected in a series circuit with voltage source 41 and switch 32B.

While the particular embodiments of the present in vention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made Without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

l. In a flame controlling and/0r indicating system of the character described comprising a blast tube for oilburning equipment through which combustion air passes, a burner nozzle within said tube, a choke ring in said tube encircling said burner nozzle, a radiation-transmitting rod having one of its ends extending through and beyond said choke ring, and a photoconductive cell within said tube and receiving flame radiation through the other end 0f said rod.

2. A system as set forth in claim 1 in which a heat shield is positioned between said burner nozzle and said cell.

3. A system as set forth in claim 1 in which an adjustable iris is positioned between said cell and said other end of said rod. f

4. A system as set forth in claim 1 in which said rod has its cylindrical wall provided with a mirror coating.

5. A system as set forth in claim l in which said rod is of quartz.

6. A system as set forth in claim l in which said rod comprises a rod of quartz and a rod of Pyrex-type glass in end-to-end relationship.

7. A system as set forth in claim l including an energizing source, a relay, and said source, relay and cell being connected in a series circuit, and means controlled by said relay for producing an indication of the condition of said flame.

8. A system as set forth in claim 1 including an energizing source, a relay, and said source, relay and cell being connected in a series circuit, and means controlled by said relay for controlling the tlow of fuel to said nozzle.

References Cited in the le of this patent UNITED STATES PATENTS 2,295,045 Mettler Sept. 8, 1942 2,958,811 Mungaard Nov. l, 1960 FOREIGN PATENTS 1,128,417 France Aug. 27, 1956 

1. IN A FLAME CONTROLLING AND/OR INDICATING SYSTEM OF THE CHARACTER DESCRIBED COMPRISING A BLAST TUBE FOR OILBURNING EQUIPMENT THROUGH WHICH COMBUSTION AIR PASSES, A BURNER NOZZLE WITHIN SAID TUBE, A CHOKE RING IN SAID TUBE ENCIRCLING SAID BURNER NOZZLE, A RADIATION-TRANSMITTING ROD HAVING ONE OF ITS ENDS EXTENDING THROUGH AND BEYOND SAID CHOKE RING, AND A PHOTOCONDUCTIVE CELL WITHIN SAID TUBE AND RECEIVING FLAME RADIATION THROUGH THE OTHER END OF SAID ROD. 